Energy storage is the fundamental element of future economy. Batteries are essential components of electric grid, electric buses, reserve power, electric tools and mobile devices. The commercialization of high performance batteries is vital for growth of any industry.
Today, the most common storage devices are lithium batteries: the energy density is high; load characteristics are reasonably good, cycle life is sufficient for many applications. Despite overall advantages, a lithium battery requires a protection circuit to maintain safe operation. The maximum charge and discharge current is limited to 2 C, and capacity deterioration can be noticeable after one year whether the battery is in use or not. The production of lithium batteries requires at least 40%-50% more investments than nickel-cadmium batteries.
A lithium battery is known as the source of three types of hazards: ignition source, fuel for existing fire, and the source of pressure pulse in the condition of thermal runaway. Recent fires with 1.5 MWh Electrovaya battery in Arizona, lithium battery problems at Boeing Dreamliner, Chevrolet Volt and Tesla motivate users to look for new storage solutions.
Rechargeable zinc batteries are considered a prospective substitute for lithium batteries. Zinc electrodes can be used in nickel-zinc, silver-zinc, zinc-air, zinc-manganese dioxide, zinc-polyaniline and other storage devices. High specific energy, low cost, safety, and vast natural resources have drawn attention to zinc as a prospective electrode for rechargeable batteries.
Zinc-air batteries are the most attractive from the point of view of energy density and low cost. However zinc-air batteries have low recharging efficiency about 0.5-0.6 and moderate power. The imperfections of zinc-air batteries can be eliminated by the use of nickel-zinc batteries with long life nickel oxide-hydroxide electrodes. (Nickel oxide-hydroxide electrodes are referenced below as nickel electrodes.)
The nickel-zinc battery is well known, and characterized with high (for alkaline battery) voltage 1.65V, recharging efficiency 0.8-0.9, and high power that exceeds performance of lithium batteries to operate at 5 C. The energy density of nickel-zinc batteries is approximately 30%-35% higher than that of nickel cadmium batteries, which production is phasing out because of cancerogenicity concerns. Nickel-zinc batteries are less expensive than their cadmium cathode analogs.
Silver-zinc battery is one of the best of energy storage devices because of the highest specific energy density and excellent power capabilities. The voltage is 1.55V, and the device can provide 40% more runtime than lithium batteries. Silver-zinc battery is alkaline based storage device, and it is free from thermal runaway and flammability of the lithium batteries. The application of silver-zinc batteries is limited by its cost and cycle life.
Major common disadvantage of all zinc rechargeable batteries is relatively short lifetime, and cycle life of the zinc anode about 300-800.
The objective of this invention is to increase lifetime and cycle life of rechargeable batteries with zinc anodes. Another objective is to propose the assembly of nickel-zinc battery cells suitable for home use and other applications.